Carburetor with fuel enrichment means



y 1967 D. L. DONOVAN 3,330,545

CARBURETOR WITH FUEL ENRICHMENT MEANS 2 Sheets-Sheet 1 Filed Oct. 13,1965 1.9 56 v INVENTOR.

flA/wa A DOA/0 VAN Arrow/5y July 11, 1967 D. 1.. DONOVAN 3,330,545

CARBURETOR WITH FUEL ENRICHMENT MEANS Filed Oct. 13, 1965 2 Sheets-Sheet2 l N VEN TOR. 04mm 1. flo/vom/v ATTORNEY United States Patent 3,330,545CARBURETOR WITH FUEL ENRICHMENT MEANS Daniel L. Donovan, Toledo, Ohio,assignor to The Tillotson Manufacturing Company, Toledo, Ohio, acorporation of Ohio Filed Oct. 13, 1965, Ser. No. 495,537 4 Claims. (Cl.261-41) This invention relates to carburetors of a character whereinvarying pressures in the fuel and air mixing passage effect delivery offuel from a fuel chamber into the mixing passage and control a fuelinlet valve to regulate fuel delivery from a supply into the fuelchamber, the fuel being mixed with air in the mixing passage and themixture conveyed to an internal combustion engine. The invention hasparticular utility in a carburetor of the diaphragm type and is adaptedfor use in other types of carbuertor, carburetors embodying theinvention being usable with either two cycle or four cycle internalcombustion engines and especially those for powering vehicles, marineengines, industrial engines and the like. In a diaphragmtype carburetorwherein varying pressures in the mixing passage influence a diaphragm tocontrol a fuel inlet valve a well as in other types of carburetors, thedelivery of fuel from the main nozzle into the mixing pas-sage tends todecrease rapidly as air flow through the mixing passage decreases. Thisoperational characteristic tends to impair the delivery of suflicientfuel for a proper fuel and air mixture at low speeds when the throttleis moved to wide open position, and to retard delivery of fuel from themain nozzle during acceleration.

The invention embraces apparatus for promoting the automatic deliveryinto the mixing passage of a carburetor of an increased amount of fuelduring periods of engine acceleration and at low engine speeds when thethrottle valve of the carburetor is in full open or near open position.

Another object of the invention resides in the provision in a carburetorof a valved passage between a main :fuel delivery orifice and a .fuelchamber for admitting additional fuel to the main orifice under lowspeed conditions at open throttle and to promote improved accelerationand additionally to interrupt flow of liquid fuel through the passagewhen the engine is operating at comparatively high speeds or wheneverthe reduced pressure in the mixing passage is suflicient to cause thevalve to close the bypass.

Another object of the invention :is the provision in a diaphragmcarburetor of a valved bypass between the fuel chamber and the maindelivery orifice into the mixing passage wherein the valve is responsiveto reduced pressure in the mixing passage to effect a closing of thevalve under certain operating conditions.

Another object of the invention resides in the provision in a diaphragmtype carburetor of a fuel bypass and pressure responsive valveconstruction arranged between the fuel chamber and the main fueldelivery orifice whereby slight reduced pressure established in themixing passage is ineffective to close the valve whereby additional fuelis delivered through the main orifice for enriching the mixture at openthrottle low engine speeds under load and to improve acceleration of theengine.

Further objects and advantages are within the scope of this inventionsuch as relate to the arrangement, operation and function of the relatedelements of the structure, to various details of construction and tocombinations of parts, elements per se, and to economies of manufactureand numerous other features as will be apparent from a consideration ofthe specification and drawing of a form of the invention, which may bepreferred, in which:

FIGURE 1 is a top plan view of a charge forming device or carburetorembodying the invention;

FIGURE 2 is a longitudinal sectional view through the carburetor, theview being taken substantially on the line 22 of FIGURE 1;

FIGURE 3 is a transverse sectional view taken substantially on the line33 of FIGURE 1;

FIGURE 4 is an end elevational view of the carburetor illustrated inFIGURE 1;

FIGURE 5 is a bottom plan view taken substantially on the line 55 ofFIGURE 4;

FIGURE 6 is a detail sectional view taken substantially on the line 6-6of FIGURE 5;

FIGURE 7 is a detail sectional view taken substantially on the line 77of FIGURE 4;

.FIGURE 8 is a fragmentary sectional view taken substantially on theline 8-8 of FIGURE 5;

FIGURE 9 is a sectional view taken substantially on the line 99 ofFIGURE 5;

FIGURE 10 is a fragmentary sectional view taken substantially on theline 10-40 of FIGURE 5, and

FIGURE 11 is a detail sectional view illustrating a modified form of theinvention.

While the invention is illustrated and described herein as embodied in acharge forming apparatus or carburetor of the diaphragm type forsupplying combustible mixture to internal combustion engines of eitherthe two cycle or four cycle type, it is to be understood that theinvention may be embodied in other types of carburetors.

Referring to the drawings in detail and initially to FIGURES 1 through4, the charge forming apparatus or diaphragm carburetor comprises a bodyor body member 10 formed of cast metal or other suitable material of anonporous character which is resistant to deterioration by hydrocarbonfuels. The body 10 is formed with a mixing passage 12 which includes anair inlet region 14, a Venturi 16, having a choke band or restriction18, and a mixture outlet region 20.

The body 10 adjacent the air inlet region is formed with bosses 22 and23 bored to journally support a shaft 24 equipped with a disc valve 26providing a choke valve arrangement for starting the engine. An arm 28is secured to the shaft 24 for manipulating the choke valve. The body 10is provided with bosses 30 bored to journally support a shaft 32 onwhich is mounted a disc type throttle valve 34 for regulating the flowof fuel and air mixture to an engine with which the carburetor may beused. An exterior portion of the throttle shaft 32 is equipped withmeans 36 for connecting an operating member 37 with the throttle shaft.

The throttle shaft 32 is provided with an arm 38, an adjustable abutmentscrew 40 supported by the body 10 being engageable with the arm 38 foradjusting the engine idling or near closed position of the throttlevalve 34.

The carburetor body has a mounting flange 42 at the outlet end 20 of themixing passage, the flange having openings accommodating bolts 44 forsecuring the carburetor to the crankcase 46 of a two cycle engine, orfor securing the carburetor to the manifold of an engine of the fourcycle type. The body 10 adjacent the air inlet region 14 has threadedopenings 48 to receive bolts for securing an air cleaner (not shown) tothe body.

The carburetor body 10 is fashioned with a comparatively shallowcircular recess providing a fuel chamber 50 adapted to contain liquidfuel. Extending across the fuel chamber 50 and forming a flexible wallthereof is a diaphragm 52 of impervious material, a circular gasket 53being associated with the diaphragm. A generally circular member orclosure plate 54 embraces the exterior major surface of the diaphragm52, the member 54 having a recess or clearance space 56 to accommodateflexing movements of the diaphragm 52.

A fuel pump body 60 is disposed beneath the member 54 with a pumpingdiaphragm 62 positioned between the 3 member 54 and pump body providinga pumping or pulse chamber 64 and a fuel chamber 66, an arrangementhereinafter described. The carburetor body 10 at a region adjacent theperiphery of the diaphragm 52 is provided with threaded openings and themembers 54, 60, the diaphragm 52 and gasket 53 fashioned with alignedopenings to receive securing screws 68 for holding these components inassembled relation illustrated in FIGURES 2, 3 and 4.

The diaphragm clearance space or dry chamber 56 in member 54 is ventedinto the air inlet region 14 of the mixing passage in the mannerillustrated in FIGURES 4 and 7. A bore in member 54 is in registrationwith a bore 71, the latter being equipped with a vent tube 72 openinginto the air inlet region 14. The space 56 is in communication with thebore 70 by a passage 74. Thus the air chamber 56 is vented throughpassage 74, communicating bores 70 and 71 and vent tube 72 to the airinlet region of the carburetor. The chamber 56 may be vented direct tothe atmosphere, if desired.

The diaphragm 52 is reinforced at its central region with disc-likemembers 73 and 75 disposed at opposite sides of the diaphragm, the discsbeing held in assembled relation with the diaphragm by a rivet 76 havinga head portion 77. The diaphragm 52 is arranged to regulate or controlflow of liquid fuel from the fuel pump or other fuel supply into theshallow fuel chamber 50. In the arrangement illustrated, connecting fuelflow passages 78, 79 are provided from the fuel pump construction to aninlet 80 of the carburetor body. Where the fuel pump, or a fuel tanksupplying fuel by gravity, is remote from the carburetor, the fuel inlet80 is connected by a tube with the fuel supply.

The carburetor body 10 is provided with a threaded bore accommodating afitting or valve cage 82 having a central passage in which is slidablydisposed an inlet valve 84 having a cone-shaped valve portion 85, thevalve portion 85 cooperating with a port provided by an annular valveseat 86 disposed in the bore accommodating the valve cage 82 forregulating or controlling fuel flow from the inlet 80 into the fuelchamber 50.

Pivotally supported or fulcrumed upon a pin 88 is a lever member 90, thepin being held in place by a threaded member 92 as shown in FIGURES 5and 10.

The long arm 94 of the lever is adapted to be engaged by the head 77 ofthe rivet 76 carried by the diaphragm, the short arm 96 of the leverengaging the lower end of the valve body 84, as shown in FIGURE 3. Anexpansive coil spring 98 bottomed in a bore provided in the upper wallof the fuel chamber 50 is disposed close to the fulcrum pin 88 andengages the long arm 94 of the lever biasing the lever in a clockwisedirection about its fulcrum, as viewed in FIGURE 3, normally urging theinlet valve 85 into seating position with the annular valve seat 86. Thefuel chamber 50 is unvented and the diaphragm is flexed solely byaspiration or reduced pressure in the mixing passage 12.

By placing the spring 98 close to the fulcrum pin 88, a comparativelystiff spring 98 may be used and yet retain a high degree of sensitivityof control of the fuel inlet valve 85. The fuel chamber 50 is made asshallow as practicable and is disposed close to the mixing passage 12 tosecure response of the diaphragm to low aspiration for delivering fuelinto the mixing passage, and to reduce to a minimum the hydrostatic headof liquid fuel on the diaphragm. The upper wall of the fuel chamber 50is fashioned with a recess 100 to accommodate swinging movement of thelever 90.

The carburetor is inclusive of a main nozzle or orifice construction forintermediate and high speed engine operation, the construction beingpreferably fashioned as a removable unit 102, shown in FIGURES 2, 6 and8, and a secondary or supplementary fuel delivery system includingengine idling and low speed orifices, shown in FIGURE 2, to facilitateidling of the engine and low speed operation. The main or primary nozzlearrange- A. ment or unit 102 includes a check valve construction forpreventing back bleeding of air into the secondary fuel delivery systemwhen the latter is delivering fuel into the mixing passage.

The main nozzle unit 102 is inclusive of a cylindricallyshaped fittingor cage 104 formed of brass or other suitable material snugly fitted orpress fitted into a bore 106, as shown in FIGURE 6. The fitting 104 isprovided with an axial bore 108 extending partially through the fitting.Arranged axially with the bore 108 is a counterbore 110 whichaccommodates a ball check valve 112. The bore 108, being of lesserdiameter than the counterbore 110, provides an annular ledge or seat 114for the ball valve 112.

Disposed in the upper or fuel delivery end of the fitting 104 is a grid118 through which fuel is delivered into the mixing passage from thepassages or bores in the fitting for normal and high speed engineoperation.

As shown in FIGURE 2, the outlet or orifice 116 of the fitting 104 opensinto the choke band region 18 of the Venturi 16 in the mixing passage.In assembly, the ball valve 112 is disposed in the counterbore 110, thegrid member 118 disposed in position and the upper peripheral region ofthe fitting swaged to hold the grid 118 in place.

The grid 118 is spaced above the ball valve 112, a sufficent distance tofacilitate movement of the valve from the seat 114 to provide for fuelflow around the valve. The ball check valve 112 is preferably fashionedof light weight material, such as nylon (polyamide resin) orpolyoxymethylene (Delrin) so that the check ball will be lifted off ofits seat under the influence of minimum lift or differential pressure.The fitting 104 is provided with a circumferential or peripheral recess120 and transversely extending bores 122 establishing communicationbetween the central bore 108 and the recess 120.

When the secondary orifice system is delivering fuel into the mixingpassage, the check ball 112 seats on the ledge 114 and thereby preventsair bleeding through the main nozzle 116 into the secondary orificesystem.

FIGURE 8 illustrates channel means and manually adjustable valve meansfor conveying and regulating fuel flow to the main fuel delivery unit102. The body 10 is fashioned with a boss 126 having a bore 128 threadedto receive the threaded portion of a manually adjustable valve or valvebody 130.

The bore 128 is in communication with a fuel chamber 50 by a passage orchannel 132 and a restricted passage 134 connects the bore 128 with theperipheral recess 120 in the fitting 104. The valve body is providedwith a needle valve portion 136 which cooperates with the restriction134 to meter or regulate flow of liquid fuel to the interior of fitting104 for delivery into the mixmg passage.

A counterbore in the boss 126 accommodates a sealing ring 140surrounding the valve body 130. The valve body 130 is provided with amanipulating head 142, and an expansive coil spring 144 is disposedbetween the head and the sealing gasket 140 to exert pressure on theseal to prevent fuel seepage or leakage of air along the valve body. Byreason of aspiration or reduced pressure in the mixing passage 12 undernormal operating conditions fuel flows from the fuel chamber 50 throughpassage 132, the bore 128, restriction 134, recess 120, transverse bores122 into the central bore 108 in the fitting for delivery past the checkvalve 112 into the mixing passage and mixed with air providing acombustible mixture.

The supplemental or secondary fuel delivery system is inclusive of asupplemental chamber 150, shown in FIG- URES 2 and 9, an engine idlingorifice 152 and a low speed orifice 154 being in communication with thesupplemental chamber 150.

The engine idling orifice 152 delivers fuel into the mixing passage onthe downstream or engine side of the throttle valve 34 for engine idlingpurposes, and the low speed orifice 154 delivers fuel into the mixingpassage when the throttle valve 34 is opened a slight amount for lowspeed engine operation. The lower end of the chamber 150 is closed by aWelsh plug 156.

FIGURE 9 illustrates the fuel channels and manually adjustable valvemeans for conveying and metering fuel flow to the engine idling and lowspeed orifices. The boss 126 is provided with a bore 162 threaded toreceive the threaded portion of a valve body 164 having a manipulatinghead 165. A channel 166 establishes communication between the fuelchamber 50 and the bore 162. A restricted passage 168 connects the bore162 with the supplemental or auxiliary chamber 150.

The valve body 164 is provided with a needle valve portion 169 whichcooperates with the restriction 168 for metering or regulating fuel flowto the supplemental chamber 150. A sealing ring 163 is biased intosealing engagement with the valve body 164 by a coil spring 167. Thus,for engine idling and low speed engine operation, fuel flows throughchannel 166, bore 162, past the needle valve 169 through restriction 168into the supplemental chamber 150 for delivery through the orifices 152and 154.

As shown in FIGURES 2, 3 and 4, the fuel pump is of the diaphragm typeand is of the character shown in Phillips Patent 2,796,838. The pumpincludes the pump body 60 which has an annular recess providing a fuelreceiving chamber 170, a cap 171 being secured to the pump body.

The cap 171 is provided with a nipple portion 172 to accommodate a tube(not shown) connected with a fuel tank or fuel supply. A screen 173extends across the chamber 170 for filtering the incoming fuel.

The pumping diaphragm 62 is connected by channel means 181 through themounting flange 42 with an opening in the engine crankcase 46 wherebythepumping diaphragm 62 is pulsated or vibrated by varying fluid pressuresin the engine crankcase for pumping fuel through the chamber 66. Thepumping diaphragm 62 is provided with an integral inlet valve 174 whichcontrols a port in communication with the fuel chamber 170, and anintegral outlet valve 175 controlling an outlet port in the pump body 60whereby fuel is pumped from the pumping chamber 66 past the outlet valve175 and through the connecting passages 78, 79 and 80 to the region ofthe inlet valve 85, shown in FIGURE 3.

The carburetor is inclusive of a valved passage or bypass between themain orifice 116 and the fuel chamber 50 for supplying additional fuelfor delivery through the main orifice to provide for increased fueldelivery into the mixing passage and enrichment of the fuel and airmixture under wide open throttle conditions at low engine speed underload and for purpose of engine acceleration. The arrangement forsupplying additional fuel is shown in FIGURES 5 and 6. The upper wall ofthe fuel chamber 50 is fashioned with a partial cylindrically-shapedrecess 176 which is in communication with a counterbore 178 Thecounterbore 178 is adjacent a smaller counterbore 180, the counterbore180 being in communication with the peripheral recess 120 in the fitting104 through a restricted passage 182. Disposed at the entrance of thefirst counterbore 178 is a screen or grid 184. Loosely disposed in thecounterbore 178 is a check valve or ball valve 186. It will be seen inFIGURE 6 that the recess 176, the connecting counterbores and therestriction 182 are axially aligned on the axis AA which is disposed atan angle relative to a horizonal plane substantially parallel with thediaphragm 52.

By disposing the bore 178 containing the check ball 186 at aninclination to a horizontal plane with the carburetor in uprightposition, the ball valve 178 normally falls by gravity to an openposition to provide a passage or bypass for fuel flow to the main nozzledirect from the fuel chamber 50 in addition to the fuel normallydelivered to 6 the main nozzle through the channel and needle valvearrangement shown in FIGURE 8.

In the operation of the arrangement of valved fuel bypass constructionwith the engine operating at normai or high speeds, the aspiration,reduced pressure or suction developed in the mixing passage by airvelocity therethrough is sufficient to lift and maintain the check ball186 onto its seat at the entrance of the counterbore 181] to interruptor block fuel flow through the bypass restriction 182 to the mainnozzle.

When the engine is operating at comparatively low speeds under load andthe throttle valve is opened rapidly there is insuificient aspiration orsuction in the Venturi acting on the main nozzle to seat the ball checkmember 186, and fuel flows direct from the fuel chamber 50 past the ballcheck valve 186 through the restriction 182 for delivery from the mainorifice construction through the main orfice outlet 116 to therebyenrichen the mixture in the mixing passage being delivered to theengine.

The fuel enriched mixture causes rapid acceleration of the engine. Asthe engine approaches the speed for which the throttle is adjusted, theaspiration or suction increases in the Venturi and the aspiration orreduced pressure, transmitted through the passages in the main orificeunit construction 102 and the restriction 182, is sufficient to maintainthe ball valve 186 in its seat and thereby interrupt fuel flow throughthe bypass restriction 182.

Under another condition, viz. the throttle being substantially open andthe engine operating under load at low speed, the aspiration or suctionin the mixing passage is insufiicient to hold the ball valve 186 in itsseat, and hence additional liquid fuel from the fuel chamber 51) flowsthrough the open restriction or passage 182 and through the main nozzle116 to provide a full power or enriched fuel and air mixture in themixing passage at low air flow.

The ball check valve 186 is always in open position during engine idlingbecause the aspiration or suction in the mixing passage at the region ofthe main orifice is of low amplitude when the throttle is in closed ornear closed position. Under conditions where the speed of the engineincreases generally in proportion to the position of opening of thethrottle valve, fluel flow through the bypass or restriction 182continues only until the pressure differential between the main nozzle116 and the fuel chamber 511 is sufiicient to lift the ball check valve186 onto its seat.

The differential pressure which will cause the ball valve 186 to belifted onto its seat is, in a measure, dependent upon the weight of theball valve and the size of the restriction 182. It is found desirable tofashion the restriction 182 of a size to provide sufiicient fuel toprovide an enriched mixture for acceleration purposes. The check ball186 may be made of a material such as nylon or Delrin as a check ballfashioned of these materials has been found to be influenced bycomparatively low aspiration or suction in the mixing passage tointerrupt the flow of liquid fuel through the bypass 182 withoutoverenriching the mixture, a condition which would lower the efficiencyof the engine in lieu of the intended purpose of securing increasedacceleration through a properly enriched mixture.

If it is desired to maintain an enriched mixture until the enginereaches a higher speed with a consequent increase in air velocitythrough the mixing passage, the ball valve 186 may be made of metal sothat higher aspiration or suction in the mixing passage is required toelevate the ball valve 186 onto its seat. The check ball 186 is made ofa material of greater density than the liquid fuel so that the ballnormally falls away from its seat by gravity.

FIGURE 11 illustrates a modified form of valved fuel passage or bypassfor admitting additional fuel into the mixing passage under certainoperating conditions. In the form shown in FIGURE 11, the valved bypassis em- '3 a bodied in the main orifice unit construction. In this formthe carburetor body 10' is fashioned with a bore 106 and snugly fittedor pressed into the bore 106 is a fitting 190 similar in shape to thefitting 104, shown in FIGURE 6. The fitting 190 is fashioned with acentral bore 192 and a peripheral recess 194, the bore being incommunication with the recess through transverse passages 196.

The peripheral recess 194 receives fuel in the normal manner from thefuel chamber 50' through a fuel channel and metering valve arrangementof the character shown in FIGURE 8 and hereinbefore described. The upperportion of the fitting 190 is fashioned with a counterbore 198 of largerdiameter in which is loosely disposed a ball valve 290 which seats onthe ledge 201 between the bore 192 and the counterbore 198.

The ball valve 200 is adapted to prevent back bleeding of air throughthe main nozzle into the secondary fuel delivery system when the latteris delivering fuel into the mixing passage.

A grid 202 is mounted in the orifice 2114 of the fitting and preventsdislodgement of the back bleeding check valve 200. The lower portion ofthe fitting 190 is provided with a counterbore 208 of larger diameterthan the bore 192 and is in communication therewith. An annular ledge orseat 210 is formed at the juncture of the bores 192 and 208 and providesa seat for a ball check valve 212 of lesser diameter than the bore 208to facilitate fuel flow around the ball valve 212 when it is out ofengagement with its seat 210.

Disposed beneath the ball check valve 212 at the lower end of thefitting 190 is a Welsh plug 214 or other closure means provided with afuel passage 216 opening into the fuel chamber 50 and preferably offsetfrom the axis of the bore 268 so that when the ball valve 212 is engagedwith the Welsh plug 212, such engagement will not impede or block flowof fuel through the passage 216. The ball valve 212 is loosely disposedin the counterbore 298 and is enabled to fall by gravity away from itsseat into contact with the Welsh plug 214 so as to permit the admissionof fuel through the passage 216 for delivery through the outlet ororifice 204 into the mixing passage.

The arrangement shown in FIGURE 11 functions substantially in the samemanner as the arrangement shown in FIGURES and 6. Under normal engineoperation the fuel is admitted into the recess 196 from a fuel channelsystem of the character shown in FIGURE 8. When the engine is idling,the ball valve 212 is in engagement with the Welsh plug 214 under theinfluence of gravity. If the throttle valve is suddenly opened, the airvelocity through the mixing passage is low and does not establishsufficient suction or aspiration to elevate the ball valve 212 onto itsseat 210.

Hence, during the period of acceleration of the engine, additional fuelflows from fuel chamber 50 through the passage 216, bores 208, 192 and1% around the ball valves 212 and 200 and is delivered through the mainorifice 204 to enrich the mixture in the mixing passage. A similarcondition obtains when the engine is operating under heavy load at lowspeed so that additional fuel flows through the bypass and past thevalves 212 and 200 into the mixing passage.

As the engine increases in speed, the aspiration or reduced pressurebecomes greater in the mixing passage to an extent as to elevate theball 212 into engagement with the valve seat 210 thereby interrupting orblocking further delivery of additional fuel by way of the bypassarrangement into the mixing passage.

During normal or high engine speeds, the ball valve 212 is maintained infuel blocking position by high aspiration or suction existent in themixing passage. The engine, during such periods receives the normalmixture of fuel delivered through the conventional channel system andpast the manual metering and regulating valve shown in FIGURE 8.

It is to be understood that the enrichment valve arrangement is notlimited to use in a diaphragm type carburetor but may be utilized incarburetors wherein float controlled valve means is employed forregulating fuel flow from a supply into the carburetor fuel chamber.

It is apparent that, within the scope of the invention, modificationsand different arrangements may be made other than as herein disclosed,and the present disclosure is illustrative merely, the inventioncomprehending all variations thereof.

I claim:

1. In combination, charge forming apparatus including a body having amixing passage, an unvented fuel chamber in said body, a flexibleimpervious diaphragm responsive to aspiration in the mixing passage andforming a wall of the fuel chamber, a fuel inlet for the fuel chamber,an inlet valve for the fuel inlet, means associated with the diaphragmengageable with the fuel inlet valve for regulating flow of liquid fuelfrom a supply into the fuel chamber, a fuel delivery orifice openinginto the mixing passage, fuel channel means in said body arranged todeliver fuel from the fuel chamber into the mixing passage through saidorifice, manually adjustable valve means for regulating fuel flowthrough said fuel channel means into the mixing passage, a fuel bypassin said body for conveying fuel from the fuel chamber into the mixingpassage independently of fuel flow regulated by the manually adjustablevalve means, the axis of the bypass being angularly arranged withrespect to the diaphragm, said bypass including a counterbore providinga valve seat in said bypass, and a ball valve of lesser diameter thanthe counterbore disposed for free movement in the counterbore, said ballvalve being loosely disposed below said valve seat and normallymaintained by gravity out of engagement with the valve seat, said ballvalve being responsive to increased aspiration in said mixing passage toengage the ball valve with the valve seat to interrupt fuel flow throughthe bypass.

2. In combination, a charge forming apparatus including a body having amixing passage, an unvented fuel chamber in said body, a flexibleimpervious diaphragm responsive to aspiration in the mixing passageforming a wall of the fuel chamber, a fuel inlet for the fuel chamber,an inlet valve for the fuel inlet, means associated with the diaphragmengageable with the fuel inlet valve for controlling flow of liquid fuelfrom a supply into the fuel chamber, orifice means opening into themixing passage, fuel channel means in said body arranged to deliver fuelfrom the fuel chamber into the mixing passage through the orifice means,means associated with said fuel channel means for metering fuel flowthrough the channel means, a fuel bypass independent of said fuelmetering means in communication with the fuel chamber and the mixingpassage, said fuel bypass including a valve chamber formed with a valveseat, a ball valve disposed for free movement in said valve chamber,said ball valve being loosely disposed below said valve seat andnormally spaced from its seat by gravity to accommodate flow ofadditional fuel through the bypass into the mixing passage under lowaspiration in the mixing passage, said ball valve being influenced byincreased aspiration in the mixing passage for interrupting fuel flowthrough said fuel bypass.

3. In combination, charge forming apparatus including a body having amixing passage, an unvented fuel chamber in said body, a flexibleimpervious diaphragm forming a wall of the fuel chamber, a fuel inletfor the fuel chamber, an inlet valve for the fuel inlet, meansassociated with the diaphragm engageable with the fuel inlet valve forregulating flow of liquid fuel from a supply into the fuel chamber, afitting in an opening in said body having an outlet providing a mainorifice for delivering fuel into the mixing passage, a secondary orificein said body opening into the mixing passage, said fitting having apassage in communication with the outlet, fuel channel means in saidbody for conveying fuel from said fuel chamber to the passage in saidfitting and to said secondary orifice, manually adjustable valve meansassociated with the fuel channel means for regulating fuel flow to thepassage in said fitting, a fuel bypass for conveying fuel from the fuelchamber direct to the fuel passage in said fitting, said fitting beingfashioned With counterbores providing two valve seats, a first valvemeans comprising a ball member in one counterbore in said fitting forpreventing back bleeding of air through the main orifice when thesecondary orifice is delivering fuel into the mixing passage, and asecond valve means comprising a ball member in the second counterborefor said fuel bypass responsive to aspiration in the mixing passage forcontrolling fuel flow through the bypass.

4. The combination according to claim 3 including a closure for the endof the fitting adjacent the second counterbore, and a fuel passage insaid closure offset from the axis of said second counterbore.

References Cited UNITED STATES PATENTS HARRY B. THORNTON, PrimaryExaminer. R. R. WEAVER, Assistant Examiner.

2. IN COMBINATION, A CHARGE FORMING APPARATUS INCLUDING A BODY HAVING AMIXING PASSAGE, AN UNVENTED FUEL CHAMBER IN SAID BODY, A FLEXIBLEIMPERVIOUS DIAPHRAGM RESPONSIVE TO ASPIRATION IN THE MIXING PASSAGEFORMING A WALL OF THE FUEL CHAMBER, A FUEL INLET FOR THE FUEL CHAMBER,AN INLET VALVE FOR THE FUEL INLET, MEANS ASSOCIATED WITH THE DIAPHRAGMENGAGEABLE WITH THE FUEL INLET VALVE FOR CONTROLLING FLOW OF LIQUID FUELFROM A SUPPLY INTO THE FUEL CHAMBER, ORIFICE MEANS OPENING INTO THEMIXING PASSAGE, FUEL CHANNEL MEANS IN SAID BODY ARRANGED TO DELIVER FUELFROM THE FUEL CHAMBER IN TO THE MIXING PASSAGE THROUGH THE ORIFICEMEANS, MEANS ASSOCIATED WITH SAID FUEL CHANNEL MEANS FOR METERING FUELFLOW THROUGH THE CHANNEL MEANS, A FUEL BYPASS INDEPENDENT OF SAID FUELMETERING MEANS IN COMMUNICATION WITH THE FUEL CHAMBER AND THE MIXINGPASSAGE, SAID FUEL BYPASS INCLUDING A VALVE CHAMBER FORMED WITH A VALVESEAT, A BALL VALVE DISPOSED FOR FREE MOVEMENT WITH A VALVE CHAMBER, SAIDBALL VALVE BEING LOOSELY DISPOSED BELOW SAID VALVE SEAT AND NORMALLYSPACED FROM ITS SEAT BY GRAVITY TO ACCOMODATE FLOW OF ADDITIONAL FUELTHROUGH THE BYPASS INTO THE MIXING PASSAGE UNDER LOW ASPIRATION IN THEMIXING PASSAGE, SAID BALL VALVE BEING INFLUENCED BY INCREASED ASPIRATIONIN THE MIXING PASSAGE FOR INTERRUPTING FUEL FLOW THROUGH SAID FUELBYPASS.